Not sure if you are coming up I-95 to I-26 to 40 or I-85 to I-26 to 40 but the first grade on I-26 is the biggest which is called the Saluda grade. It is 3 lanes going up hill with the truckers usually using the 2 right lanes. There are a couple of other grades, one being the Green River Gorge grade which is as steep but not as long. Once on 40, the mountain gorge from Asheville to Exit 407 (Pigeon Forge/Sevierville) is pretty flat but since it's a gorge, it's 2 lanes with the truckers required to use the right lane only so yes, sometimes it can be a little slow. Since it's a mountain gorge, it does have some curves but no switchbacks. There is a rest stop which we called the top of the world half way thru the gorge. In the old days, we used to run the gorge at 80 mph (posted back then at 70) but now it's posted at 55 mph. Be careful and have fun.